2-2 Biology: Properties of Water

Cohesion

Attraction between molecules of the same substance

Adhesion

Attraction between molecules of different substances

Solution

A mixture where all components are evenly distributed

Solvent

The substance in which the salute dissolves (water)

Solute

The substance that is dissolved

Suspension

A mixture where materials do not dissolve, but remain suspended

pH scale

Indicates the concentration of H plus ions in solution

Acid

Any compound that forms H plus ions in solution that is less than pH seven

Base

A compound that produces hydroxide ions in solution

Buffer

Weak acids or bases that can react with strong acids or bases to prevent sharp sudden changes in pH

Structure of a Water Molecule

2 hydrogen atoms and 1 oxygen atom that are joined by a covalent bond

When a water molecule is polar

There is an uneven distribution of charge

How do hydrogen bonds form between water molecules

Because of polarity

Why is water often called the ‘universal solvent’

Because it dissolves more substances than any other liquid

What effect does polarity have on the way Water molecules interact with each other

Polarity allows water molecules to be attracted to each each other leading to cohesion and hydrogen bonding

What is the pH scale used to measure

It is used to measure acidity in a substance. It measures the hydrogen ion conceptions

What pH value represents neutral solution

7

Example of acids

Stomach acid and lemon juice

Example of base

Soap and bleach

Why are buffers important

They keep pH levels stable in organisms, maintaining homeostasis